Methods and Apparatuses for Navigating the Subaracnhnoid Space

ABSTRACT

Disclosed is a method of navigating a spinal subarachnoid space in a living being, that includes percutaneously introducing a device into the spinal subarachnoid space at an entry location. The device has a first passageway that is sized to slidably receive, and work with, at least a guidewire. The device can be a catheter or a sheath. The method can also include advancing the device within the spinal subarachnoid space at least more than 10 centimeters from the entry location. Alternatively, the method can include advancing the device within the spinal subarachnoid space to facilitate intracranial access with a second device introduced through the first passageway. Also disclosed is a device suited for attachment to a patient&#39;s skin, such as a sheath, that includes an elongated member, a skin-attachment apparatus having a flexible skin-attachment flap, and a valve apparatus.

CROSS REFERENCE TO RELATED APPLICATION

This patent application is a continuation of Ser. No. 09/905,670, filedon Jul. 13, 2001, now U.S. Pat. No. 7,455,666, which is incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to surgical methods and medicaldevices. More particularly, it concerns methods and apparatuses usefulin navigating the subarachnoid space, including the spinal and theintracranial subarachnoid spaces. It also concerns medical devices, suchas sheaths, that are suited for attachment to the skin.

2. Description of Related Art

During the 20^(th) century, brain neurosurgery has advanced via theintroduction of microsurgical techniques, the development of new toolssuch as aneurysm clips, and the description of new operative approaches.Surgeons have developed elegant mechanisms to remove parts of the bonesmaking up the skull (craniotomy) and operate on structures deep withinthe brain while attempting to minimize complications relating to theapproach. [See, for example, Fries et. al., 1996.] Furthermore, thesurgical approach to the intracranial and spinal subarachnoid space hashistorically consisted of the skin incision, dissection to either thecranium or spinal bony covering, removal of some bone, and dissectionthrough the meninges to gain access to the neurological structures.While imaging modalities became integrated into diagnostic evaluations,only at the end of the last century were significant attempts made tointegrate computed tomography, angiography, and most recently magneticresonance (MR) scanning into the actual surgical procedures.

Unfortunately, craniotomy has limited the applicability of such imagingmodalities because the surgeon cannot simultaneously stand at thepatient's head and conveniently operate on the brain via craniotomy,maintain sterility, and scan the brain using a large scanning apparatusthat requires the patient to be held within it. There are theoreticallimits to the ability to conveniently perform such surgery usingcurrently-available imaging devices due to a conflict between the meansof acquiring images and the means of operating on the brain.Furthermore, in conventional neurosurgery, while the brain surface isreadily available underlying a craniotomy, the approach to deeperstructures is progressively more invasive in terms of retraction injury(i.e., the brain is often retracted after the craniotomy to facilitateaccess to different areas in and around the brain) or even the need toremove brain tissue to gain access.

During the last 20 years, the development of endovascular neurosurgeryhas resulted in the creation of specialized devices for applicationwithin arteries. These devices include not only catheters andguidewires, but also embolic materials that can be introduced viacatheters, thereby enabling the enhancement of some procedures that areperformed via craniotomy following embolization, and thereby eliminatingthe need for craniotomy altogether in other cases. However, thesetechniques have heretofore been limited to the intravascular space(i.e., the space within blood vessels) because that was seen as the onlyavailable route of access for catheterization of the intracranialcontents.

Extravascular access to locations within the head for the purpose offacilitating the kinds of procedures heretofore performed following acraniotomy has not been reported to the inventor's knowledge. Thesubarachnoid space, which is a compartment that contains the body of thespinal cord and cerebrospinal fluid (CSF)—a fluid that fills andsurrounds the ventricles (cavities) of the brain and the spinal cord,and acts as a lubricant and a mechanical barrier against shock—is onesuch extravascular route.

Some authors have described experimental data using endoscopy in thesubarachnoid space. An endoscope is a tube with a light and a lens onthe end that can be used to view various regions within a body. Onegroup from Sweden utilized a relatively large (4 millimeter)bronchoscope (a type of endoscope) to travel the length of thesubarachnoid space to eventually visualize the contents of the posteriorfossa, as well as gain access to the ventricular system. [Stefanov et.al., 1996.] These studies were performed in cadavers and involveddissection to the lumbar space and introduction of the bronchoscope fromthat location, using only endoscopic guidance. Applications in theclinical setting were not advocated.

A group from Japan utilized a smaller endoscope in cadavers to accessonly the subarachnoid space around the spinal cord and posterior fossa.[Eguchi et. al., 1999.] No attempt was made to access either theventricles or the supratentorial cisterns. The endoscopes used also hadno directional capability. Uchiyama et. al. (1998) used a “myeloscope”(a type of endoscope) that was sufficiently small (0.5-2 mm) to safelyaccess the spinal subarachnoid space without injuring the spinal cord ina group of patients. Neither of these articles discusses catheterizingthe subarachnoid space, whether for the purpose of facilitatingintracranial access or otherwise. Furthermore, neither group attemptednavigation of the subarachnoid space using catheters and guidewires orother means to more precisely control device placement or otherinstrument insertion.

Amar et. al. (2001) recently described a technique of catheterizing thespinal epidural space for the introduction of medication. However, thattechnique did not involve catheterization of the subarachnoid space, norwas it performed for the purpose of facilitating intracranial access.Other techniques of delivering anesthetics and other therapeutic agentsto the subarachnoid space using catheters are described in U.S. Pat.Nos. 5,085,631 and 5,470,318.

The techniques disclosed in these patents do not involve advancing thecatheter toward the head of the patient after the catheter is introducedinto the subarachnoid space. Nor do they involve steps that facilitateintracranial access. Neither patent discloses using catheters forintroducing other medical devices through the passageways in thosecatheters for the purpose of facilitating intracranial access.

The inventor is aware of other techniques for delivering medicaments tothe subarachnoid space using a catheter. However, of these, noneinvolved the use of catheters for the purpose of facilitatingintracranial access. [See, for example, Delhaas, 1996.]

In addition, medical devices (e.g., sheaths) that are used with theforegoing techniques to facilitate the introduction of endoscopes andcatheters into the subarachnoid space are not well-suited for use withimaging modalities such as MR scanning. Generally, once a sheath is inplace within a patient, other devices such as endoscopes and catheterscan be introduced into the patient through the passageway within thesheath. In other words, once the sheath is in place, one end of thesheath is located beneath the patient's skin while the other end sticksout of the patient's skin, thereby allowing the surgeon to introduce,for example, an endoscope or catheter into the patient through thesheath's passageway. The manipulations that cause these introductions tooccur are carried out at the end of the sheath that is positionedoutside of the patient. However, a traditional sheath is sized andconfigured such that it does not extend very far outside of a patientonce it has been inserted into a desired location. As a result, themanipulations of other medical devices introduced through the sheathcannot feasibly take place while the patient is positioned within an MRscanner (which mainly consists of large magnets) because there simply isnot enough of the sheath sticking out of the patient to work with.Furthermore, this same shortcoming would impede a surgeon's ability touse one or more robotic devices to assist in or completely perform thesemanipulations.

Based on the foregoing, new methods of facilitating intracranial accessthat do not involve the shortcomings of craniotomy, and that can bemonitored or guided via various imaging modalities are needed. Newmethods of facilitating intracranial access via devices introducedthrough non-endoscopic devices are also needed. Furthermore, new medicaldevices useful for establishing access to areas such as the subarachnoidspace, and that can be used with robotic instruments or while thepatient is positioned within an MR scanner are needed.

SUMMARY OF THE INVENTION

The present invention addresses the shortcomings of the prior art byproviding methods of navigating the subarachnoid space that does notinvolve the removal of bone. In addition, the present invention providesa medical device that is suited for attachment to the skin, and whichenhances the flexibility afforded to the operating carrying out thepresent methods.

In one respect, the invention is a method of navigating a spinalsubarachnoid space in a living being. The method includes percutaneouslyintroducing a device into the spinal subarachnoid space at an entrylocation. The device has a first passageway sized to slidably receive,and work with, at least a guidewire. The method also includes advancingthe device within the spinal subarachnoid space at least more than 10centimeters from the entry location.

In one embodiment, method also includes removing a portion of the brainof the living being. The living being contains cerebrospinal fluid, andin another embodiment, the method also includes flushing at least somecerebrospinal fluid in order to remove blood from that cerebrospinalfluid. In another embodiment, the method also includes inducinghypothermia in at least some brain tissue. In another embodiment, themethod also includes accessing at least one ventricle located within thehead with a second device introduced through the first passageway of thedevice. In another embodiment, the method also includes draining atleast one ventricle located within the head after accessing theventricle.

In another embodiment, the device includes a second passageway sized toslidably receive, and work with, at least a guidewire. In anotherembodiment, the method also includes introducing an endoscope throughthe first passageway of the device. In another embodiment, the deviceincludes a first sub-elongated member that has the first passageway, anda second sub-elongated member coupled to the first sub-elongated member,and the second sub-elongated member has the second passageway. Inanother embodiment, the device also includes a braiding material wrappedaround the first and second sub-elongated members.

In another embodiment, a cross section taken along the device has ashape that is non-circular. In another embodiment, the method alsoincludes altering the temperature of at least some brain tissue using apumping apparatus. In another embodiment, the method also includesdelivering medication to an intracranial subarachnoid space. In anotherembodiment, the device includes a wall to which anelectroencephalography electrode is attached. In another embodiment, thedevice includes a wall to which a sensor useful for monitoring abiochemical property is attached, and the method also includesmonitoring either pH, glucose concentration, oxygen tension, carbondioxide concentration, or sodium concentration using the sensor. Inanother embodiment, the device includes a wall to which a thermal sensoruseful for monitoring temperature is attached, and the method alsoincludes monitoring temperature using the thermal sensor.

In another embodiment, the method also includes introducing an apparatusthrough the first passageway of the device; and applying electriccurrent, heat, or cryothermal stimulation to a tissue within the livingbeing using the apparatus. In another embodiment, the method alsoincludes introducing a radioactive pellet through the first passagewayof the device; and placing the radioactive pellet within the livingbeing in order to irradiate a tumor. In another embodiment, the methodalso includes introducing a detector through the first passageway of thedevice; and placing the detector within the living being. In anotherembodiment, the method also includes monitoring a physiologic orbiochemical property using the detector.

In another embodiment, the method also includes introducing apenetration apparatus through the first passageway of the device, thepenetration apparatus including an outer sleeve element and an innerpuncture element, the outer sleeve element and the inner punctureelement being slidably coupled together; and puncturing the pia materusing the penetration apparatus. In another embodiment, the method alsoincludes creating a lesion in the brain of the living being. In anotherembodiment, the advancing step of the method is achieved via a roboticdevice. In another embodiment, the method also includes monitoring theposition of the device for a period of time using magnetic resonanceimaging, fluoroscopy, endoscopy, computed tomography, thermal imaging,sonography, or any combination of these. In another embodiment, themethod also includes introducing an electrode through the firstpassageway of the device; and placing the electrode within the livingbeing. In another embodiment, the electrode is an electroencephalographyelectrode and the placing includes placing the electroencephalographyelectrode proximate brain tissue. In another embodiment, the method alsoincludes introducing material through the first passageway of thedevice; and placing the material proximate a cranial nerve to assist intreating a neurologic condition. In another embodiment, the method alsoincludes introducing genetic material through the first passageway ofthe device; and placing the genetic material within the living being toassist in treating a neurologic condition.

In another respect, the invention is a method of navigating a spinalsubarachnoid space in a living being. The method includes percutaneouslyintroducing a device into the spinal subarachnoid space. The device hasa first passageway sized to slidably receive, and work with, at least aguidewire. The method also includes advancing the device within thespinal subarachnoid space to facilitate intracranial access with asecond device introduced through the first passageway.

In one embodiment, the method also includes removing a portion of thebrain of the living being. The living being contains cerebrospinalfluid, and in another embodiment, the method also includes flushing atleast some cerebrospinal fluid in order to remove blood from thatcerebrospinal fluid. In another embodiment, the method also includesinducing hypothermia in at least some brain tissue. In anotherembodiment, the method also includes accessing at least one ventriclelocated within the head with a second device introduced through thefirst passageway of the device. In another embodiment, the deviceincludes a second passageway sized to slidably receive, and work with,at least a guidewire. In another embodiment, the device includes a firstsub-elongated member that has the first passageway, and a secondsub-elongated member coupled to the first sub-elongated member, and thesecond sub-elongated member has the second passageway. In anotherembodiment, the device includes a wall to which a sensor useful formonitoring a biochemical property is attached, and the method alsoincludes monitoring either pH, glucose concentration, oxygen tension,carbon dioxide concentration, or sodium concentration using the sensor.

In another embodiment, the method also includes introducing an apparatusthrough the first passageway of the device; and applying electriccurrent, heat, or cryothermal stimulation to a tissue within the livingbeing using the apparatus. In another embodiment, the method alsoincludes introducing a radioactive pellet through the first passagewayof the device; and placing the radioactive pellet within the livingbeing in order to irradiate a tumor. In another embodiment, the methodalso includes introducing a detector through the first passageway of thedevice; and placing the detector within the living being. In anotherembodiment, the method also includes monitoring a physiologic orbiochemical property using the detector. In another embodiment, theadvancing step of the method is achieved via a robotic device. Inanother embodiment, the method also includes monitoring the position ofthe device for a period of time using magnetic resonance imaging,fluoroscopy, endoscopy, computed tomography, thermal imaging,sonography, or any combination of these.

In yet another embodiment, the method also includes introducing anelectrode through the first passageway of the device; and placing theelectrode within the living being. In another embodiment, the electrodeis an electroencephalography electrode and the placing includes placingthe electroencephalography electrode proximate brain tissue.

In another respect, the invention is a method of navigating a spinalsubarachnoid space within a living being. The method includesintroducing a non-endoscopic device into the spinal subarachnoid space.The non-endoscopic device has a passageway. The method also includesadvancing the non-endoscopic device within the spinal subarachnoid spaceand toward the head of the living being to facilitate intracranialaccess with a second device introduced through the passageway; andmonitoring the position of the non-endoscopic device for a period oftime using an imaging modality other than an endoscope. In this document(including the claims), a “non-endoscopic device” is one that is not anendoscope. In this document (including the claims), an “endoscope” is adevice to which a lens has been directly attached (usually at a tip ofthe device). A device such as one of the catheters or sheaths discussedbelow that has a passageway through which an endoscope is passed andwith which an endoscope is used does not become an endoscope as aresult.

In another respect, the invention is a medical device suited forattachment to a patient's skin. The medical device includes a memberthat has two ends and a first passageway sized to slidably receive, andwork with, at least a guidewire; and a skin-attachment apparatus that isconfigured to be coupled to the member at a coupling location that isbetween the two ends. The skin-attachment apparatus has a flexibleskin-attachment flap configured for attachment to the skin. The medicaldevice also includes a valve apparatus that is configured to be coupledto one end of the member. The valve apparatus and the skin-attachmentapparatus define a flexible member portion between them when both arecoupled to the member.

In one embodiment, the coupling location is variable during a procedure.In one embodiment, the medical device also includes a secondskin-attachment apparatus that is configured to be coupled to the memberat a second coupling location that is spaced apart from the couplinglocation. In one embodiment, the flexible member portion has a length ofat least 2 centimeters. In one embodiment, a cross section taken alongthe member has a shape that is non-circular. In one embodiment, themember has a second passageway. In one embodiment, the member includes afirst sub-elongated member that has the first passageway, and themedical device also includes a second sub-elongated member coupled tothe first sub-elongated member, and the second sub-elongated member hasthe second passageway.

In another embodiment, the member is bendable, and is configured toretain a shape after being bent. In another embodiment, the valveapparatus is configured for use with a robotic device. In anotherembodiment, the member has a length, and a stiffness that varies alongthe length. In another embodiment, the two ends of the member are firstand second ends; the valve apparatus is configured to be coupled to thefirst end; the member has a distal portion near the second end; and thedistal portion includes a wall that has an electroencephalographyelectrode therein. In another embodiment, the two ends of the member arefirst and second ends; the valve apparatus is configured to be coupledto the first end; the member has a distal portion near the second end;and the distal portion includes a wall that has a sensor useful formonitoring a biochemical property. In another embodiment, thebiochemical property is pH, glucose concentration, oxygen tension,carbon dioxide concentration, or sodium concentration. In anotherembodiment, the two ends of the member are first and second ends; thevalve apparatus is configured to be coupled to the first end; the memberhas a distal portion near the second end; and the distal portionincludes a wall that has a thermal sensor useful for monitoringtemperature.

In yet another embodiment, the medical device also includes a flush linecoupled to the valve apparatus. In another embodiment, the flexibleskin-attachment flap includes padding material. In another embodiment,the valve apparatus includes a hub configured for attachment to othermedical devices.

In another respect, the invention is a sheath suited for attachment to apatient's skin. The sheath includes a member that has a first end, asecond end, and a first passageway sized to slidably receive, and workwith, at least a guidewire. The sheath also has a skin-attachmentapparatus that is configured to be coupled to the non-rigid member at acoupling location that is between the first and second ends, but atleast 2 centimeters from the first end. The skin-attachment apparatushas a flexible, padded skin-attachment flap configured for attachment tothe skin. The medical device also includes a valve apparatus that isconfigured to be coupled to the first end of the member. The valveapparatus and the skin-attachment apparatus define a flexible memberportion between them when both are coupled to the member. The couplinglocation may be varied either prior to or after attachment of the sheathto the skin.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the present methodsand apparatuses. The present methods and apparatuses may be betterunderstood by reference to one or more of these drawings in combinationwith the description of illustrative embodiments presented herein. Thesedrawings illustrate by way of example and not limitation, and they uselike references to indicate similar elements.

FIG. 1 illustrates selected areas of the central nervous system andmedical devices introduced into the spinal subarachnoid space using thepresent methods.

FIGS. 2A and 2B are enlarged versions of the lumbar region of the spineshown in FIG. 1, and illustrate a medical device suited for attachmentto the skin that was placed using the present methods.

FIG. 3 is a top view of a medical device suited for attachment to theskin and illustrated as a sheath.

FIGS. 4-9 illustrate different embodiments of the skin-attachmentapparatus that is coupled to the sheath shown in FIG. 3.

FIG. 10 is a cross-sectional view of an embodiment of an elongatedmember of one of the present medical devices suited for attachment tothe skin, illustrating a non-circular shape.

FIG. 11 is a cross-sectional view of an embodiment of an elongatedmember of one of the present medical devices suited for attachment tothe skin, illustrating two passageways sized to slidably receive, andwork with, at least a guidewire.

FIG. 12 is an end view showing two sub-elongated members coupledtogether.

FIG. 13A illustrates sub-elongated members of different lengths.

FIGS. 13B-H are partial side views illustrating different embodiments ofends of two coupled sub-elongated members.

FIG. 14 is a partial side view illustrating a detector attached to theoutside surface of one of the present medical devices.

FIG. 15 is a cross-sectional view showing the detector depicted in FIG.14 being coupled to a communication device illustrated as a wirepositioned in the wall of the medical device.

FIG. 16 illustrates an operator applying the present methods to apatient positioned within an MR scanner.

FIG. 17 illustrates a detector being placed in brain tissue using thepresent methods.

FIG. 18 depicts one embodiment of a penetration apparatus.

FIG. 19 is a partial side view depicting one embodiment of twosub-elongated members coupled together with a braiding material.

FIG. 20 is a partial side view depicting one embodiment of a catheterwrapped in braiding material.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As a preliminary matter, it should be noted that in this document(including the claims), the terms “comprise” (and any form thereof, suchas “comprises” and “comprising”), “have” (and any form thereof, such as“has” and “having”), and “include” (and any form thereof, such as“includes” and “including”) are open-ended transitional terms. Thus, athing that “comprises,” “has,” or “includes” one or more elementspossesses those one or more elements, but is not limited to onlypossessing those one or more elements. For example, a device “having afirst passageway sized to slidably receive, and work with, at least aguidewire” is a device that has, but is not limited to only having, thedescribed first passageway. In other words, the device possesses thefirst passageway, but is not excluded from possessing additionalpassageways or other elements that are not listed.

The present methods involve navigating the subarachnoid space, includingthe spinal subarachnoid space. In some embodiments, the intracranialsubarachnoid space is also navigated. The present methods facilitateintracranial access via the subarachnoid space. For example, using thepresent methods, a first device may be introduced into the subarachnoidspace to facilitate intracranial access with another device introducedthrough one or more passageways located within the first device. In thisdocument (including the claims), “intracranial access” means access tothe space within the head that is above the foramen magnum. In addition,intracranial subarachnoid space is the subarachnoid space located abovethe foramen magnum, and the spinal subarachnoid space is thesubarachnoid space located below the foramen magnum, though the spacesare contiguous without a physical barrier between them. In this document(including the claims), a step that involves moving one device “tofacilitate intracranial access” with another device introduced throughthe first device is a step that is taken with the intention of makingintracranial access with the second device possible.

The present minimally-invasive methods offer new routes of access forboth brain and spine surgery that involve no craniotomy or bone removal.Advantageously, the present methods can be performed with the operatorstanding remote from the patient's head. The route of access is astandard puncture of the spinal subarachnoid space, such as in thelumbar spine. Then, techniques conventionally used in intravascularprocedures are applied in order to navigate the subarachnoid space,including the intracranial subarachnoid space in some cases. The presentmethods should have fewer problems with exposure of the brain toinfectious agents and offer an opportunity for navigation of manystructures without brain retraction or removal to achieve access.

Turning to the figures, FIG. 1 illustrates certain aspects of thecentral nervous system of a patient that have been navigated using thepresent techniques. Specifically, FIG. 1 illustrates dural membrane 10,spinal cord 12, subarachnoid space 14, lumbar vertebrae L1, L2, L3, L4,and L5, sacrum 16, and brain 18, including cerebellum 20. FIG. 1 alsoillustrates as sheath 24 a medical device suited for attachment to skin22, which includes elongated member 26, first end 28, second end 30,skin-attachment apparatus 32, valve apparatus 36 coupled to first end28, and flush line 38. As used in this document (including the claims),“elongated” simply means having a length. Skin-attachment apparatus 32includes flexible skin-attachment flap 34 configured for attachment (andactually attached as shown) to skin 22. Further, skin-attachmentapparatus 32 is configured to be coupled to elongated member 26 at alocation along elongated member 26 described in this document (includingthe claims) as a “coupling location.” FIG. 1 illustrates thatskin-attachment apparatus 32 and valve apparatus 36, which are bothcoupled to elongated member 26, define flexible member portion 40between them.

As shown in FIG. 1, elongated member 26 includes a first passageway thatis sized to slidably receive, and work with, at least a guidewire. Inthis document (including the claims), a passageway that is “sized toslidably receive, and work with, at least a guidewire” means that thepassageway is configured for use in normal operation with a medicaldevice that can be the size of at least a guidewire. Thus, a passagewayso sized is configured for use in normal operation with a guidewire, andmay also be configured for use in normal operation with larger medicaldevices, including certain sheaths, catheters, and dilators. As shown inFIG. 1, another device having a first passageway that is sized toslidably receive, and operate with, at least a guidewire is illustratedas catheter 42, which has been percutaneously introduced intosubarachnoid space 14 at entry location 50 through the first passagewayof elongated member 26. Guidewire 44 is shown in FIG. 1 as having beenpercutaneously introduced into subarachnoid space 14 at entry location50 through the first passageways of both catheter 42 and elongatedmember 26. As used in this document (including the claims), “introducinga device into the subarachnoid space” means causing the device to passthrough the boundary that defines the spinal subarachnoid space. Theboundary need not be physical, so the device does not need to be incontact with the subarachnoid space. Thus, and for example, passing aguidewire or a catheter through the passageway in a sheath that ispositioned within the subarachnoid space amounts to introducing thatguidewire or catheter into the subarachnoid space so long as thatguidewire or catheter passes across the boundary that defines where thesubarachnoid space begins. Furthermore, as used in this document(including the claims), “percutaneously introducing” a device means tointroduce the device without first cutting away bone through, forexample, craniotomy or drilling burr holes.

Prior to percutaneously introducing sheath 24 into subarachnoid space 14at entry location 50, an operator may direct a guidewire through skin 22and dural membrane 10 and into subarachnoid space 14, and morespecifically the spinal subarachnoid space, in order to facilitate theintroduction of sheath 24. This guidewire introduction may be achieved,for example, by directing a needle through the skin and the duralmembrane between any of the lumbar vertebrae. The spaces betweenadjacent vertebrae are known as interspaces, such as the L1-2 interspacelabeled as element 46.

While FIG. 1 illustrates introduction into the subarachnoid space (andspecifically into the spinal subarachnoid space) in the lumbar region,entry locations may be made in other regions, including the thoracic andcervical regions of the spine. Thus, devices such as catheters, sheaths,and guidewires (including those illustrated in FIG. 1) may pass throughthe following interspaces: C1-2, C2-3, C3-4, C4-5, C5-6, C6-7 (i.e., thecervical interspaces), T1-2, T2-3, T3-4, T4-5, T5-6, T6-7, T7-8, T8-9,T9-10, T10-11, and T11-12 (i.e., the thoracic interspaces). With theneedle in place, a guidewire may be introduced into the spinalsubarachnoid space through a passageway (sometimes referred to as a“lumen”) within the needle. The guidewire may then be directedsuperiorly and advanced within the spinal subarachnoid space and towardthe patient's head to a desired location. The position of the guidewirewithin the patient, including within the various regions of thesubarachnoid space, may be monitored using any suitable imagingmodality, such as magnetic resonance imaging, fluoroscopy, endoscopy,computed tomography, thermal imaging, sonography, or any combination ofthese. Moreover, these imaging modalities can be used throughout aprocedure to monitor the various positions of other medical devices,provided that the right conditions exist (such as sufficientradiopacity, etc.)

After introducing a guidewire, such as guidewire 44, into thesubarachnoid space, the operator may dilate the tract created by theguidewire using one or more medical devices suited for that purpose,such as dilators. This may be done after removing the needle.Alternatively, a suitably structured sheath may be introduced over theguidewire for the same dilation purpose and also to facilitateintracranial access with a second device introduced through thepassageway of the sheath. If an operator uses a dilator, a medicaldevice such as sheath 24 may be passed over the dilator, and the dilatorcan then be removed through the passageway of the sheath.

Following sheath placement, techniques applied during procedures such asangiography may be used to navigate the subarachnoid space, includingthe spinal and intracranial subarachnoid spaces. In this regard, anotherguidewire may be introduced through the sheath and into the subarachnoidspace with a tip that is directed either anteriorly or posteriorly inrelation to the spinal cord. A medical device such as a catheter maythen be introduced over the guidewire to facilitate intracranial accessusing a device introduced through the passageway of the catheter.

The navigation described above, including one or more of the steps forintroducing the various medical devices into the subarachnoid space andadvancing those devices within the subarachnoid space and, sometimes,toward the head of the patient, may be achieved in whole or in partusing a robotic device. Furthermore, the representative applications ofthe present methods discussed below may be carried out in whole or inpart using a robotic device. Potential advantages of using a roboticdevice in this fashion pertain, for example, to navigating throughneural tissue. The pial membrane surrounding the brain forms a barrierto penetration, and once the membrane is punctured, there is essentiallyno resistance to navigation offered by cerebral tissue. Using a roboticdevice to assist with navigation of the cerebral tissue may bebeneficial given the great extent to which the movements of a catheteror guidewire can be controlled using a robotic device and viewed usingan imaging modality.

Turning next to FIG. 2A, an enlarged view of a small portion of thecentral nervous system is illustrated, and sheath 24 is shown positionedwithin the subarachnoid space 14. As shown in FIG. 2A, subarachnoidspace 14 is the spinal subarachnoid space. The spinal subarachnoid spaceis located within the bony canal created by the vertebrae and isdifferent than the intracranial subarachnoid space, which is locatedabove the foramen magnum, as described above. As shown, sheath 24 waspercutaneously introduced into the spinal subarachnoid space throughdural membrane 10 at entry location 50, and subsequently advancedthrough the spinal subarachnoid space and toward the head of the patientto facilitate intracranial access by both catheter 24 and guidewire 44.Skin-attachment apparatus 32, which is configured to be coupled to and,in fact, is coupled to, elongated member 26 of sheath 24, is shown asbeing attached to skin 22 using sutures 54 (only one of which is shown)placed through openings 56 (only one of which is shown) in flexibleskin-attachment flap 34. Securing mechanism 52 is shown in FIG. 2A asbeing used with skin-attachment apparatus 32 to secure the position ofskin-attachment apparatus 32 along elongated member 26. Advantageously,the coupling location of skin-attachment apparatus 32 to elongatedmember 26 may vary, thereby increasing the versatility of sheath 24 bycomparison to sheaths with fixed skin-attachment apparatuses.Furthermore, by spacing apart skin-attachment apparatus 32 from valveapparatus 36, flexible member portion 40 is defined between the two.

Flexible member portion 40 affords the operator many advantages becauseit gives him/her the ability to introduce devices through the one ormore passageways of sheath 24 at a location that is remote (i.e., spacedapart) from both the location at which the sheath is attached to theskin and the location at which the sheath enters the skin. For example,some patient motion during the operation can be absorbed by flexiblemember portion 40. Also, because the length of flexible member portionmay be adjusted, the operator can position him or herself remotely fromthe patient when performing the various steps of the present methods andwhile permitting the position of various instruments to be monitored viaimaging modalities such as magnetic resonance imaging (MRI). Thus,having a suitable length, flexible member portion 40 will allowextension of elongated member 26 from the area of the patient that willbe inaccessible during placement of the patient in an MR scanners.

The length of the present flexible member portions, and the distancebetween one of the present skin-attachment apparatuses and the first endof one of the present elongated members (which distance will differ fromthe length of the present flexible member portion based on the length ofthe valve apparatus in question) can be any distance suited to theparticular operation, including 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5,6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5,14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5,21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5,28, 28.5, 29, 29.5, 30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5,35, 35.5, 36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, 40, or morecentimeters. Additional suitable distances include 41, 42, 43, 44, 45,46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,64, 65, 66, 67, 68, 69, and 70 centimeters, or even more if theparticular application warrants further removal of the operatingphysician from the insertion point in the skin. Furthermore, the lengthof flexible member portion 40 can be adjusted to suit the use of sheath24 with a robotic device.

Moving to FIG. 2B, it shows a view similar to that depicted in FIG. 2A.Specifically, FIG. 2B illustrates sheath 24, which has beenpercutaneously introduced into subarachnoid space 14 (which, as shown,is spinal subarachnoid space) at entry location 50. From entry location50, sheath 24 has been advanced (as shown by the dotted lines) adistance from that entry location to a second location 51. This distanceis illustrated in FIG. 2B in terms of D1, which is the distance alongthe path taken by sheath 24. D1 can be determined by measuring thelength of sheath 24 advanced beyond entry location 50. This distance isalso illustrated in terms of D2, which is the straight-line distancebetween entry location 50 and second location 51. This distance is alsoillustrated as D3, which is the absolute distance toward the head thatsheath 24 has been advanced between entry location 50 and secondlocation 51. D3 can be determined by measuring the distance between aplane intersecting entry location 50 and oriented substantiallylaterally across the longitudinally-oriented patient and a planeintersecting second location 51 and oriented substantially laterallyacross the longitudinally-oriented patient.

In this document (including the claims), advancing a device a distancefrom an entry location means that the device is advanced a distanceconsistent with any of D1, D2, and D3. Thus, advancing a device at leastgreater than 10 centimeters from an entry location means that the deviceis advanced at least more than 10 centimeters (e.g., any distance thatis greater than 10 centimeters, including 10.1 centimeters, etc.)according to the distance along the path taken by the device (i.e., D1),that the device is advanced at least more than 10 centimeters accordingto the straight-line distance from the entry location (i.e., D2), orthat the device is advanced at least more than 10 centimeters accordingto the absolute distance in the direction of advancement from the entrylocation (i.e., D3). Suitable distances that the devices disclosedherein that have passageways sized to slidably receive, and operatewith, at least a guidewire (such as sheath 24 and catheter 42) may beadvanced within the spinal subarachnoid space from the entry location ofthe device consistent with the present methods include 1, 1.5, 2, 2.5,3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.1, 10.2,10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.5, 12, 12.5, 13, 13.5,14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5,21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5,28, 28.5, 29, 29.5, 30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5,35, 35.5, 36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, 40, or morecentimeters. Furthermore, distances that the devices disclosed hereinthat have passageways sized to slidably receive, and operate with, atleast a guidewire (such as sheath 24 and catheter 42) may be advancedwithin the spinal subarachnoid space consistent with the present methodsand that are greater than at least 10 centimeters from the entrylocation of the device include 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7,10.8, 10.9, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5,17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5,24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30, 30.5,31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, 35, 35.5, 36, 36.5, 37, 37.5,38, 38.5, 39, 39.5, 40, or more centimeters. Further still andconsistent with the present methods, the devices disclosed herein thathave passageways sized to slidably receive, and operate with, at least aguidewire (such as sheath 24 and catheter 42) may be advanced within thespinal subarachnoid space distances from the entry locations of thedevices greater than at least 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5,15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5,22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5,29, 29.5, 30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, 35, 35.5,36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, 40, or more centimeters.

FIG. 3 illustrates a top view of sheath 24. As illustrated in a cut-awaysection of FIG. 3, elongated member 26 has a first passageway 58 that issized to receive, and work with, at least a guidewire. Valve apparatus36, which is configured to be coupled to and, in fact, is coupled tofirst end 28 of elongated member 26, provides a membrane 60 that extendsacross first passageway 58 in a way that allows other devices to beintroduced through passageway 58 while preventing fluid from flowing outof sheath 24 through first end 28. Within this document (including theclaims), a “valve apparatus” is any apparatus that, when coupled (eitherdirectly or indirectly) to elongated member 26, is capable of sealingone or more of the passageways (such as first passageway 58) ofelongated member 26 against fluid trying to flow out through theparticular passageway in a direction out of a patient. Although membrane60 is shown as extending across first passageway 58 at a location withinfirst passageway 58, those of skill in the art having the benefit ofthis disclosure will understand that membrane 60 could also bepositioned outside of first passageway 58 and achieve the same function.For example, although not shown, those of skill in the art having thebenefit of this disclosure will understand that membrane 60 could beformed as a rubber gasket situated between two elements that screw intoeach other and vary an opening within membrane 60, thereby providing anadjustable opening valve. Valve apparatus may be coupled to elongatedmember 26 using any suitable means, including a threaded connection,friction fit, interlocking parts, a clamp, glue, integral formation orother means of permanent attachment, or the like. In addition, valveapparatus 36 may be configured, as it is in FIG. 3, to allow forattachment of flush line 38. This may be accomplished in anyconventional fashion, including through the use of a protrusion that isformed as part of valve apparatus 36 and extends away from it (notshown) to which a flush line may be coupled. Valve apparatus 36 may alsobe configured to allow for fluid communication between flush line 38 andfirst passageway 58. Alternatively, valve apparatus may also beconfigured to allow for fluid communication between flush line 38 and apassageway within elongated member 26 other than first passageway 58.Furthermore, valve apparatus 36 may be configured with hub 62 that isconfigured for attachment to other medical devices such as guidewires,sheaths, catheters, and introducers. The hub may, for example, take theform of a male or female Luer lock piece.

Although only one skin-attachment apparatus 32 is illustrated in thepresent figures, certain operations may benefit from the use of two ormore such apparatuses. Accordingly, two, three, four, five, or moreskin-attachment apparatuses configured to be coupled to elongated member26 may be coupled to and used with elongated member 26. Each of theseskin-attachment apparatuses may be coupled to elongated member 26 atcoupling locations spaced apart from the ends of elongated member 26.One combination of skin-attachment apparatuses includes permanentlyattaching one to elongated member 26, and coupling anotherskin-attachment apparatus in between the permanently-attachedskin-attachment apparatus and a valve apparatus coupled to the first endof the elongated member such that the coupling location of the secondskin-attachment apparatus is variable. Furthermore, each skin-attachmentapparatus may have a flexible skin-attachment flap that is configuredfor attachment to the skin of a patient. In this regard, while openings56 are shown in flexible skin-attachment flap 34 for attaching theflexible skin-attachment flap to the skin of a patient, it will beunderstood that any suitable manner of configuring the flap forattachment to the skin may be used, including the use of a temperaturesensitive adhesive, a repositionable adhesive, clips (such as smallalligator clips), tape, glue, and the like.

FIGS. 4-9 show different embodiments of skin-attachment apparatus 32. InFIG. 4, skin-attachment apparatus 32, which is configured to be coupledto elongated member 26 at a coupling location and which includesflexible skin-attachment flap 34, is coupled to elongated member 26 suchthat it is permanently attached to elongated member 26. This may beaccomplished by securing flexible skin-attachment flap 34 to elongatedmember 26 through gluing, integral formation, or the like.

FIG. 5 shows skin-attachment apparatus 32 coupled to elongated member 26in a way that permits the coupling location of skin-attachment apparatusto elongated member 26 to vary prior to or after attachment ofskin-attachment apparatus to a patient's skin. Specifically,skin-attachment apparatus 32 includes flexible skin-attachment flap 34,secondary flap 66, and securing mechanisms 52, which serve to tightenthe flaps against elongated member 26 when the mechanisms are engaged.Securing mechanisms may take the form of clips (such as small alligatorclips), clamps, flaps that snap together, string, or any other suitablemeans of temporarily securing flaps 34 and 66 around elongated member 26in a way that prevents elongated member 26 from moving relative to theflaps until securing mechanisms 52 are disengaged. Padding material,such as a sponge, gelatin-like material, or trapped air may be placed inspaces 68 defined by flaps 66, 34, and elongated member 26, in order tomake attachment of skin-attachment apparatus 32 more comfortable topatients placed in supine positions.

FIGS. 6-8 show skin-attachment apparatuses 32 coupled to elongatedmember 26 using only one securing mechanism 52. In addition,skin-attachment apparatus 32 in FIG. 6 includes adhesive 70, instead ofopenings 56 shown in other figures, that is useful in attaching flexibleskin-attachment flap 34 to a patient's skin. In FIG. 7, flexibleskin-attachment flap 34 contains padding material 72 (as may any of thepresent flexible skin-attachment flaps), which is useful as describedabove. In both FIGS. 6 and 7, flexible skin-attachment flaps 34 arepositioned between elongated member 26 and securing mechanisms 52. Incontrast, FIG. 8 shows that securing mechanism 52 may be in directcontact with elongated member 26. In the embodiment shown in FIG. 8,flexible skin-attachment flap 34 may be secured to securing mechanism 52using any suitable means, including glue, integral formation, and thelike.

Although not shown in FIGS. 4-9, it should be understood that a flexibleskin-attachment flap 34 may be configured in the form of a flap that isfolded over elongated member 26 and snapped together, the mating snapsserving as securing mechanism 52.

Turning to FIG. 9, the embodiment of skin-attachment apparatus 32 shownincludes padding material 72 within flexible skin-attachment flap 34,and may include the same in space 68. Flaps 66 and 34 shown in both FIG.5 and FIG. 9 may be attached to each other using any suitable meansdescribed in this document.

FIGS. 10, 11 and 12 illustrate different embodiments of elongated member26 of sheath 24. While these figures are described in terms of elongatedmember 26 and, hence, sheath 24, the embodiments discussed are equallyapplicable to devices such as catheter 42 depicted in FIG. 1, which maybe introduced through the passageways discussed in FIGS. 10-12.

FIG. 10 illustrates a cross section of elongated member 26, revealingthat it can have a shape at a given cross section that is non-circular.Advantageously, an elongated member 26 having such a shape along anyportion of its length may be well-suited to navigating certain regionswithin the subarachnoid space that are wider in one dimension than inanother. Suitable shapes of cross sections taken at a particularlocation along an elongated member include oval, and figure-eightshapes. Furthermore, the present elongated members, and the presentsub-elongated members discussed below, may have cross-sectional shapesthat vary along the length of the member.

FIG. 11 illustrates another cross section of elongated member 26,revealing that it can have both first passageway 58 and secondpassageway 74. Like first passageway 58, second passageway 74 can besized to slidably receive, and work with, at least a guidewire.Moreover, elongated member 26 can have additional such passagewaysconsistent with the present methods and apparatuses. Additionally, whilethe passageways described in this document (including the claims) mayextend through openings that coincide with the ends of the particulardevices in question (such as sheath 24 and catheter 42 shown in FIG. 1),the openings within the present medical devices that serve to define thepresent passageways may be located in positions other than the ends ofthe present medical devices. Thus, a sheath or a catheter that has oneor both ends closed may nevertheless have a passageway as that term isused in this document (including the claims) so long as two openings tothe outside of the device exist that serve to define the passageway. Forexample, one of the present devices could have a passageway defined byopenings positioned within the wall of the device. In addition, twopassageways could share a common opening, regardless of the location ofthe common opening. However, if the passageway in question is restrictedto being sized to slidably receive, and work with, at least a guidewire,the positioning of the openings in question must satisfy this conditionas well.

Turning next to FIG. 12, there is shown elongated member 26 having twosub-elongated members 76 and 78 that are coupled together using couplingdevice 80, which allows the operator to snap the pieces of tubingtogether. Other means for coupling sub-elongated members 76 and 78 mayalso be used, such as interlocking parts that are integrally formed withthe sub-elongated, interlocking parts that are attached to thesub-elongated members, adhesives that serve to secure the sub-elongatedmembers together but that allow them to be repositioned and re-secured,melting of the sub-elongated members together, glue, and the like.Alternatively, sub-elongated members 76 and 78 may be joined, as bybonding during manufacture, such that a cross-sectional configuration ofthem resembles that shown in FIG. 12, only without a coupling device 80interposed between sub-elongated members 76 and 78. Sub-elongated member76 has first passageway 58, and sub-elongated member 78 has secondpassageway 74. In this document (including the claims), “a sub-elongatedmember” can, but need not, have a perfectly round cross section. Thus,both sub-elongated members 76 and 78 could have cross sections at anylocation along their length with shapes like the ones depicted in FIG.10.

Furthermore, as shown in FIG. 13A, sheath 24 can include elongatedmember 26, which can have sub-elongated members 76 and 78 that possessdifferent lengths. As shown, sub-elongated member 76 has first end 28and second end 30, and sub-elongated member 78 has first end 82 andsecond end 84. FIG. 13A also shows that valve apparatus 36 may becoupled to both sub-elongated members, as may be skin-attachmentapparatus 32. Furthermore, end 84 is closed, and sub-elongated member 78has an opening 86 located within the wall of sub-elongated member 78that together with the opening at first end 82 of sub-elongated member78 serves to define second passageway 74.

Moving ahead to FIG. 13H, the same shows that the sub-elongated membersof sheath 24 depicted in FIG. 13A may alternatively be arranged suchthat one of the sub-elongated members has multiple openings 86, as shownin sub-elongated member 76. Sub-elongated member 76 has a closed secondend 30 in FIG. 13H. As explained below, fluid may be introduced throughone passageway to a desired location, and withdrawn through anotherpassageway. The configuration of sheath 24 illustrated in FIG. 13H maybe used during such a procedure.

FIGS. 13B-G illustrate different embodiments of the shapes of secondends 30 and 84 of sub-elongated members 76 and 78, respectively. FIG.13B shows that second end 30 of sub-elongated member 76 may be offsetfrom second end 84 of sub-elongated member 84. FIG. 13B also shows thatsecond end 30 of sub-elongated member 76 may be beveled, or tapered,into sub-elongated member 80, thereby reducing the chance that sheath 24will “hang up” on other structures prior to reaching its intendeddestination. This same benefit may be realized using the configurationof sheath 24 (via sub-elongated members 76 and 78) shown in FIGS. 13C,13D, and 13G. The configurations illustrated in FIGS. 13E and 13F may beused as the application warrants.

Currently, catheters are available that have compound wall constructionsthat impart a variable stiffness along the length of the catheter.Catheters are also available with reinforcing material braided into thewall of the catheter to give the catheter greater strength andresistance to kinking. The present devices such as catheter 42 andsheath 24 may have lengths and stiffnesses that vary along thoselengths, and they may have walls that include braided materials therein.Also, the present devices such as catheter 42 and sheath 24 may bebendable, and may retain a shape after being bent.

As those of skill in the art will understand, the size of a givenpassageway of one of the present devices (such as sheath 24 or catheter42) may be sized appropriately for a given application. Diameters for apassageway within a given device (such as sheath 24, and specificallyelongated member 26, and catheter 42) may, for example, be chosen fromsizes that include 0.008, 0.009, 0.010, 0.011, 0.012, 0.013, 0.014,0.015, 0.016, 0.017, 0.018, 0.019, 0.020, 0.021, 0.022, 0.023, 0.024,0.025, 0.026, 0.027, 0.028, 0.029, 0.030, 0.031, 0.032, 0.033, 0.034,0.035, 0.036, 0.037, 0.038, 0.039, 0.040, 0.041, 0.042, 0.043, 0.044,0.045, 0.046, 0.047, 0.048, 0.049, 0.050, 0.051, 0.052, 0.053, 0.054,0.055, 0.056, 0.057, 0.058, 0.059, 0.060, 0.061, 0.062, 0.063, 0.064,0.065, 0.066, 0.067, 0.068, 0.069, 0.070, 0.071, 0.072, 0.073, 0.074,0.075, 0.076, 0.077, 0.078, 0.079, 0.080, 0.081, 0.082, 0.083, 0.084,0.085, 0.086, 0.087, 0.088, 0.089, 0.090, 0.091, 0.092, 0.093, 0.094,0.095, 0.096, 0.097, 0.098, 0.099, and 0.10 inches. These samedimensions may, for example, serve as the size of either the widest ormost narrow dimension of a passageway of one of the present devices(such as sheath 24, and specifically elongated member 26, and catheter42) that has a non-circular shape. The outer diameter of the presentdevices (such as sheath 24, and specifically elongated member 26, andcatheter 42) may, for example, be chosen from sizes that include 1, 2,3, or 4 millimeters. These same dimensions may, for example, serve asthe size of either the widest or most narrow dimension of the outersurface of one of the present devices (such as sheath 24, andspecifically elongated member 26, and catheter 42) that has anon-circular shape.

As explained with reference to FIG. 1, for example, the present devices(such as sheath 24 and catheter 42) enter the spinal subarachnoid spaceafter passing through dural membrane 10. In order to close duralmembrane 10 after a procedure is complete, the present devices (such assheath 24, and specifically elongated member 26, and catheter 42) mayhave a dural closure apparatus coupled to it. The dural closureapparatus may be configured to be coupled to the device in question,and, in fact, may be coupled to it. The dural closure apparatus may beconfigured to close the dural membrane as the device is withdrawn fromthe spinal subarachnoid space. In one embodiment, the dural closureapparatus may be configured to effect closure through movement of aneedle, or other suture-delivering apparatus, that is actuated by theoperator to cause a suture to be placed through the dura. In anotherembodiment, the dural closure apparatus may be configured to effectclosure through injection of a chemical compound that seals the hole inthe dura after the device is withdrawn. One example of a dural closureapparatus that may be modified and coupled to one of the present devicesis THE CLOSER (commercially-available from Perclose, Inc., an AbbotLaboratories Company, 400 Saginaw Drive, Redwood City, Calif. 94063).

FIG. 19 illustrates an embodiment of sheath 24 (which, of course, isequally applicable to catheter 42) in which sub-elongated elements 76and 78 exist, wherein braiding material 130 (which can be a wire) iswrapped around both sub-elongated elements along the length of thesub-elongated elements (the total length not being shown). Such wrappingappears as a figure eight when viewed from the top. The braidingmaterial may be wrapped as tightly or as loosely as the applicationwarrants, and the tightness of the wrapping may vary along the length ofsheath 24, thereby imparting the sheath with a variable stiffness and,therefore, flexibility. The same type of wrapping may be applied to acatheter having only one passageway, as illustrated in FIG. 20. There,the wrapping may be achieved using a single wire that is placed incontact with the wall of catheter 42 at roughly the mid-point 132. Then,the two halves of braiding material 130 may be crisscrossed to achievethe desired braiding, varying the tightness of the wrapping as desiredto affect the stiffness of catheter 42. Alternatively, one end ofbraiding material may be placed in contact with catheter 42 near the endshown in FIG. 20, and the braiding may be achieved by winding the freeend of the braiding material once around the catheter, then back up soas to cross the already-formed loop, then back down slightly further,and back up in the same fashion, repeating the process to achieve thedesired braiding. Again, the tightness of the wrapping (which may bethought of as the closeness of the braiding material segments to eachother) may be varied to vary the stiffness of the catheter.

The braiding pattern used may affect the MR-visibility of the resultingcatheter or sheath. The subarachnoid space is filled with CSF that isrelatively static and is of very high signal intensity on T2-weightedimages. While a material that presents a signal void on MR could not beseen on either T1- or T2-weighted fluoroscopy in the vascular space(flowing blood has a signal void in either of these settings), amaterial that has a signal void is very conspicuous on T2-weightedimaging in the subarachnoid space. Platinum is a metal that isappropriate for enhancing the MR-visibility of the present devices.Additionally, other metals having low signal intensity may beappropriate. For example, there is a non-ferromagnetic form of stainlesssteel that is used in some needles for biopsy under MR guidance (Cook,Inc.). Also, there is an alloy of nickel and titanium (nitinol) that isused for guidewires and has been used in catheter braiding in the past(Target Therapeutics) that may have desirable signal characteristics.These materials may be used as markers on the present devices, and forbraiding material 130. In addition, stainless steel, which is currentlyused in some catheter braiding by Cordis, may be used as braidingmaterial 130. Kevlar may also be used for braiding material 130.

Medical devices such as sheaths and catheters that have theconfigurations discussed in FIGS. 11 and 12 (i.e., that have two or morepassageways) may enable the use of an endoscope in one passageway toobserve, for example, a manipulation conducted using a device introducedthrough the other passageway, or even the position of the othersub-elongated member that has the other passageway. Medical devices suchas sheaths and catheters that have the configurations discussed in FIGS.11 and 12 (i.e., that have two or more passageways) may also permit afluid to be introduced in one passageway and withdrawn via the otherpassageway. Medical devices such as sheaths and catheters that have theconfigurations discussed in FIGS. 11 and 12 (i.e., that have two or morepassageways) may allow the introduction of a guidewire in one passagewayand another, therapeutic device in the other passageway. Interactionbetween functions conducted via each passageway may be achieved suchthat the functions work together, or compliment each other, to achieve atherapeutic goal.

Furthermore, medical devices such as sheaths and catheters that have theconfigurations discussed in FIGS. 11 and 12 (i.e., that have two or morepassageways) have vascular applications, too. For example, there arecurrently instances in aneurysm treatment in which one catheter isintroduced via one femoral artery for placement within an aneurysm andanother catheter is introduced via the other femoral artery forintroduction of a balloon across an aneurysm neck. Using a device otherthan a balloon to assist the aneurysm coiling, an apparatus may beintroduced via one passageway of a medical device such as a sheath orcatheter that has one of the configurations discussed in FIGS. 11 and 12(i.e., that has two or more passageways) to improve an aneurysm neckwhile a coil is introduced via the other passageway, thus achieving viaa single femoral artery access that currently requires bilateral access.Furthermore, this aneurysm embolization may be achieved using a sheathor catheter that includes 2 sub-elongated members whose distal portionsare spaced apart from each other, as in a “Y” shape.

FIG. 18 illustrates a penetration apparatus 120 that is useful inpenetrating various membranes that may be encountered using the presentmethods. Penetration apparatus 120 includes outer sleeve element 122,outer sleeve element hub 124 coupled to outer sleeve element 122, innerpuncture element 126, and inner puncture element hub 128 coupled toinner puncture element 126. Outer sleeve element hub 124 may beconfigured to be slidably coupled to inner puncture element 126 (suchthat outer sleeve element 122 may slide along, and then be lockedagainst, inner puncture element 126), and inner puncture element hub 128may be configured to be slidably coupled to another device introducedthrough the passageway (not shown) of inner puncture element 126. Innerpuncture element may be provided with a passageway sized to slidablyreceive, and operate with, at least a guidewire.

One membrane that may be punctured by operating penetration apparatus120 is the pia mater—a membrane surrounding the brain that is fragile insome locations and tough in others. Distal tip 130 of inner punctureelement may be configured to be sharp enough to penetrate the pia materat any location therealong without exerting a degree of force ormanipulation that results in either tearing of brain tissue ordistortion of brain tissue prior to penetration. In operation, a device(such as sheath 24 or catheter 42) may be percutaneously introduced intothe spinal subarachnoid space at an entry location, the device having afirst passageway sized to slidably receive, and operate with, at least aguidewire; the device may be advanced within the subarachnoid space atleast more than 10 centimeters from the entry location, or to facilitateintracranial access with a second device introduced through the firstpassageway; penetration apparatus 120 may be advanced through the firstpassageway of the device, and a membrane, such as the pia mater, may bepunctured using penetration apparatus 120. More specifically,penetration apparatus 120 may be advanced along a guidewire, or it maysimply be advanced through the first passageway, to the edge of themembrane; inner puncture element 126 may be further advanced until itpunctures the membrane; inner puncture element may then be retractedinto outer sleeve element 122 and penetration apparatus 120 advancedthrough the plane of the punctured membrane, or outer sleeve element 122may be advanced over inner puncture element 126 through the plane of thepunctured membrane. Outer sleeve element 122 may then act as a guidewirefor a device such as catheter 42 as the same advances into the brainsubstance.

The material that may be used for the inner and outer elements ofpenetration apparatus 120 may, for example, be metallic or polymeric,such as plastic. Suitable materials for both outer sleeve element 122and inner puncture element 126 include a nickel-titanium alloy, such asnitinol, that is treated to enhance its radiopacity. Alternatively,stainless steel may be used for either element, which can be plated withgold or platinum to enhance radiographic visibility. If an imagingmodality such as MRI or radiographic visualization (e.g., fluoroscopy),that imaging modality used may impact the materials used in theconstruction of the elements of penetration apparatus 120.

Another embodiment of penetration apparatus 120 that is not shown inFIG. 18 differs from the embodiment shown in FIG. 18 in the manner inwhich the inner and outer elements 126 and 122 are interrelated. In thisadditional embodiment, inner puncture element 126 is coupled to outersleeve element 122 with a mechanism that allows inner puncture elementto be “fired,” or advanced rapidly, a few millimeters to achieve rapidpenetration. In yet another embodiment of penetration apparatus 120 notshown in FIG. 18, inner puncture element 126 is coupled to outer sleeveelement 122 using threads to allow for finely-controlled advancement ofinner puncture element 126.

The present methods will offer many advantages over conventional methodsof surgically accessing the intracranial and spinal subarachnoid space,which have historically consisted of the skin incision, dissection toeither the cranium or spinal bony covering, removal of some bone, anddissection through the meninges to gain access to the neurologicalstructures. For example, the present methods will avoid a craniotomy anda brain retraction, which are typical for conventional approaches tobrain surgery; the present methods will enable operators to surgicallyapproach the brain from a remote location (such as from a lumbarpuncture, for instance); they will make it possible to perform suchsurgery in an MR scanner without interference from magnets in thesurgical field; they will allow access to areas of the brain that aredifficult to reach from a craniotomy approach; and the present methodsit may enable some types of procedures (subarachnoid space lavage, etc.)not easily performed via craniotomy.

Representative Applications of the Present Methods

The following representative applications may be performed using devicessuch as catheter 42 and sheath 24, and further using any embodiment ofthose devices depicted in FIGS. 1 and 10-13H. Thus, anytime that adevice such as catheter 42 or sheath 24 is referenced below in relationto the representative applications, it will be understood that versionsof that device depicted in FIGS. 10-13H may be used for the givenapplication. Depending on the application, the devices used may betreated so as to maximize their visibility via a given imaging modality,such as MRI or radiography (e.g., fluoroscopy).

Furthermore, it will be understood that for a given application, it maybe feasible to introduce one device into the subarachnoid space at oneentry location, and later, or simultaneously, introduce another deviceinto the subarachnoid space at a different entry location, thereafterusing the devices together to achieve a therapeutic result. For example,in altering the temperature of at least some brain tissue, discussedbelow in greater detail, it may be possible to introduce a fluid throughthe passageway of one device introduced into the subarachnoid space(such as the spinal subarachnoid space) at one entry location, andwithdrawing fluid through the passageway of another device introducedinto the subarachnoid space (such as the spinal subarachnoid space) atanother entry location. As another example, in flushing CSF as describedbelow, it may be beneficial to use two passageways of a sheath orcatheter having multiple passageways to deliver fluid to a target area.Further, this may be achieved using a sheath or catheter that includes 2sub-elongated members whose distal portions are spaced apart from eachother, as in a “Y” shape. Fluid may be withdrawn through the passagewayof a device introduced at a different entry location, or fluid may bewithdrawn through a third passageway within the sole sheath or catheter.

Flushing of Cerebrospinal Fluid to Help Alleviate Vasospasm

The present methods can be used in the treatment of subarachnoidhemorrhage. A major complication of subarachnoid hemorrhage isvasospasm, which is related to the presence of blood in the subarachnoidspace surrounding cerebral blood vessels. One treatment that is usedneurosurgically to help alleviate vasospasm entails the lavage of thecerebrospinal fluid within the subarachnoid space with both saline andwith hemolytic agents to remove the blood. Using the present methods, itmay be feasible from a percutaneous spinal approach to catheterize thesubarachnoid space in the region of a hemorrhage or clot and performlavage from that approach without craniotomy. For example, afterintroducing a device (such as sheath 24 or catheter 42 discussed inrelation to FIG. 1) into the spinal subarachnoid space at an entrylocation, the device having a passageway sized to slidably receive, andwork with, at least a guidewire, and after advancing that device withinthe spinal subarachnoid space a distance from the entry location, salineand/or material having hemolytic agents may be transferred through thepassageway of the device toward the region of the hemorrhage or clot inorder to flush the relevant cerebrospinal fluid. This flushing may alsobe achieved with a second device introduced through the passageway ofthe first device.

Modifying the Temperature of at Least Some Brain Tissue

The present methods can be used to modify the temperature of at leastsome brain tissue. Such a modification may be achieved by flushingselected brain tissue with a fluid that may be temperature-controlled,such as saline, which fluid is introduced through a device introducedinto the spinal subarachnoid space. For example, after introducing adevice (such as sheath 24 or catheter 42 discussed in relation toFIG. 1) into the spinal subarachnoid space at an entry location, thedevice having a passageway sized to slidably receive, and work with, atleast a guidewire, and after advancing that device within the spinalsubarachnoid space a distance from the entry location, the temperatureof at least some brain tissue may be modified by introducing atemperature-controlled fluid, such as saline, through the passageway ofthe device to the selected brain tissue. This may be particularlyeffective using a device that has at least two passageways. Theintroduction of fluid in this manner may also be achieved with a seconddevice introduced through the passageway of the first device.

One example of modifying the temperate of at least some brain tissue isinducing hypothermia in at least some brain tissue. The potentialbeneficial effects of hypothermia in protection against injury are wellknown, both in the public domain and in the medical literature. The mostcommonly encountered instance in the uncontrolled environment isprobably in near drowning. In these situations, survival is enhanced incold water because the metabolism is slowed and hypoxia is bettertolerated.

In neurosurgical practice, hypothermia is used therapeutically toprolong cerebral vascular occlusion times that can be tolerated duringaneurysm surgery. However, most traditional neurosurgical techniques areunable to create isolated cerebral hypothermia. Thus, whole-bodyhypothermia is used, often in association with circulatory arrest, withall the attendant risks.

A pumping apparatus may be utilized in the process of modifying thetemperature of at least some brain tissue to assist in maintainingpressures and temperatures within the subarachnoid space. This pumpingapparatus may be coupled to the device through which the fluid isintroduced. This pumping apparatus may include 2independently-controlled, calibrated pumps that may be coupled to a hubadapter coupled to, for example, the device through which the fluid isintroduced. To control the intracranial fluid volume, the volume offluid pumped into the subarachnoid space may be matched by an equalvolume that is withdrawn from the subarachnoid space. This pumpingapparatus may be configured to achieve this balance with flow monitorsand flow controls, even in circumstances in which the outflow may beachieved without introducing negative pressure at the outflow site.Further, in this regard, this pumping apparatus may be configured tooperate with pressure monitors and pressure controls that enable boththe measurement of intracranial pressures and the manipulation of thesame. In addition, this pumping apparatus may be configured to operatewith temperature monitors and temperature controls that enable both themeasurement of intracranial temperatures and the manipulation of thesame. In this regard, the pumping apparatus may be configured to operatewith temperature monitors and temperature controls that enable both themeasurement of infused fluid temperatures and the manipulation of thesame.

Flow rates as low as a fraction of a cubic centimeter per second or ashigh as multiple cubic centimeters per second may be achieved with thispumping apparatus, though pressures exceeding 200 millimeters mercuryare considered unlikely since this would exceed intracranial pressureslikely to be compatible with life. Infusate (i.e., infused liquid)temperatures varying between 32 and 110 degrees Fahrenheit may beachieved using this pumping apparatus.

Monitoring Physiologic and Biochemical Properties

The present devices that have passageways sized to slidably receive, andwork with, at least a guidewire (including those illustrated as sheath24 and catheter 42 in FIG. 1) may also have walls that have monitorstherein. In this regard, FIG. 14 illustrates a portion of device 90having wall 92 and detector 94 attached to wall 92. Detector 94,although shown as attached to the exterior of wall 92, may be embeddedwithin wall 92 beneath the outer surface of wall 92 in certainembodiments, depending, for example, on the depth of detector 94 belowthe outer surface and the type of material from which wall 92 is made.In such an instance, device may be described as having wall 92 and adetector 94 “in” or “within” wall 92, or “therein.” Further, wall 92 mayhave an opening, and detector 94 may be attached to the inside surfaceof wall 92 and extending across that opening, provided properprecautions are taken to avoid damaging detector 94 as device 90 isnavigated. Additionally, the location of detector 94 may be varied, frombeing at an end of device 90, to being located at any position alongwall 92.

Detector 94 may be an electroencephalography electrode useful formonitoring electrical activity (i.e., an attribute). Detector 94 may bea sensor useful for monitoring a biochemical property (i.e., anattribute) such as pH, glucose concentration, oxygen tension, carbondioxide concentration, or sodium concentration. Thus, one of thosebiochemical properties may be monitored using the sensor. Detector 94may be a thermal sensor useful for monitoring temperature (i.e., anotherattribute). Thus, temperature, such as of a fluid or a temperature, maybe monitored using the thermal sensor. Detector 94 may also be usefulfor monitoring neurotransmitter concentration (i.e., an attribute).Thus, neurotransmitter concentration may be monitored using thedetector. In this document (including the claims), an element such as adetector, which may take the form of a sensor, that is “useful formonitoring” something need only play a role in the monitoring, and neednot completely perform all the steps necessary to achieve themonitoring. Also, in this document (including the claims), monitoring anattribute “using” a sensor or a detector means that the sensor ordetectors is involved, or plays a role, in the monitoring, but need notbe the only device used to achieve the monitoring

FIG. 15 is a cross sectional view of device 90, showing that detector 94may be coupled to a communication device that is illustrated as wire 96embedded within wall 92. It will be understood to those of skill in theart having the benefit of this disclosure that the communication device(in this case, wire 96) may alternatively be secured to the outsidesurface of wall 92 as is detector 94, or to the inside of the wall. Thecommunication device may travel along the length of device 90 anysufficient distance, and may exit, or extend away from, wall 94 at anysuitable location, including prior to the end of device 90 that is notshown in FIG. 14, at a hub coupled (whether permanently or otherwise) tothe end of device 90 that is not shown, at the end of device 90 that isnot shown, and at a valve apparatus (such as valve apparatus 36illustrated, for example, in FIG. 3) coupled to the end of device 90that is not shown. The communication device can then be linked to astation that processes the signal from the detector that travels alongthe communication device and that is useful in monitoring andcontrolling the detected attribute. The pumping apparatus disclosedherein may include that station. The station may be configured to recorddata that it collects and/or generates in monitoring and/or controllingthe detected attribute on any suitable media, including paper andelectronic data. The communication device can also take the form of awireless communication using, for example, radio waves or otherelectromagnetic means of transmission.

FIG. 16 illustrates some of the benefits of the present methods. FIG. 16illustrates a patient positioned in MR scanner 100 and on top of slidingtable 102. Operator 104 is positioned remotely from the target areabeing scanned such that the magnets within MR scanner 100 do notinterfere with his or her manipulations. Sheath 24 is shown as beinginserted into the patient, and a communication device illustrated aswire 96 is shown traveling from outside of valve apparatus 36 to station106. Wire 96 is coupled to a detector (not shown) attached to the wallof the elongated member 24. The hidden detector may be anelectroencephalography electrode useful for monitoring electricalactivity. The hidden detector may be a sensor useful for monitoring abiochemical property such as pH, glucose concentration, oxygen tension,carbon dioxide concentration, or sodium concentration. The hiddendetector may be a thermal sensor useful for monitoring temperature. Thehidden detector may also be useful for monitoring neurotransmitterconcentration. Station 106 may be configured to record data that itcollects and/or generates in monitoring and/or controlling the detectedattribute on any suitable media, including paper and electronic data.Also, a second communication device in the form of wire 108 isillustrated as exiting station 106 and traveling to an undisclosed areawhere another operator can view the data generated and collected bystation 106.

The same types of monitoring that may be achieved using a detectorattached to a device such as sheath 24 or catheter 42 (which isillustrated in the form of device 90 in FIG. 14), may also be achievedusing a detector or detectors implanted in brain tissue or in thesubarachnoid space. FIG. 17 illustrates detector 112 that is positionedintracranially. FIG. 17 shows brain 18 inside of head 110, and furthershows that catheter 42 may have a wall in which detector 94 is located.FIG. 17 also illustrates that a communication device in the form of wire96 is coupled to detector 94 and embedded within the wall of catheter42, as indicated by the dashed lines. A detector delivery mechanismillustrated as wire 114 is shown as being coupled to detector 112. Thiscoupling may be achieved through any suitable means, includingelectromagnetic means, and mechanical means such as clips, andtemperature- or pressure-sensitive adhesives, and the like. Detector 112may be coupled to wire 114 in a way that will allow the detector to bedetached from wire 114 once detector 112 has reached its intendeddestination. In such an embodiment, detector 112 may wirelesslycommunicate with a station like station 106 illustrated in FIG. 16.Alternatively, the detector delivery mechanism illustrated as wire 114may remain coupled to detector 112 and serve as a communication devicebetween detector 112 and a remote station. In any embodiment, detector112 should be configured to slidably move within the passageway ofcatheter 42. Devices, such as catheter 42, may have passageways at leastas large as 0.016″ in the widest dimension and may be used to introducedetectors 112 to a desired location. Detector 112 may include ananchoring mechanism for retaining its position once delivered. Thisincludes an anchoring mechanism that deploys once detector 112 exitscatheter 42; such an anchoring mechanism may have a non-tubularconfiguration. For example, one suitable anchoring mechanism that isalso used in vascular systems involves “hooks” or “barbs” located at thetips of wire members of devices, which hooks engage the walls of vesselsto hold the device in place. Such hooks may also be used as an anchoringmechanism to engage the dura in instances in which detector 112 isimplanted in the subarachnoid space. Another suitable anchoringmechanism would be a flared end on detector 112, resembling conventionalflared configurations on the tips of conventional ventricular shuntcatheters. Such an anchoring mechanism would be useful in instances inwhich a detector 112 is placed either in brain tissue or in a catheterdestined for a ventricle. Like detector 94, detector 112 may be anelectroencephalography electrode useful for monitoring electricalactivity. Detector 112 may also be a sensor useful for monitoring abiochemical property such as pH, glucose concentration, oxygen tension,carbon dioxide concentration, or sodium concentration. Detector 112 maybe a thermal sensor useful for monitoring temperature. Detector 112 mayalso be useful for monitoring neurotransmitter concentration.

In addition to the embodiments illustrated in FIGS. 14, 15, and 17,multiple detectors 94 may be attached to the inside or outside surfacesof the wall of one of the present devices (such as sheath 24 or catheter42), or placed within the wall of one of the present devices, in orderto better monitor the various attributes discussed above. Thus, 2, 3, 4,5, 6, 7, 8, 9, 10, or more detectors may be placed on or in one of thepresent devices. Furthermore, a single communication device (such aswire 96) may be used to link multiple detectors to a station.Additionally, each of the sub-elongated members illustrated in FIG. 13may be provided with the detectors discussed above, in the mannersdiscussed above. Thus, and by way of example, both of the sub-elongatedmembers shown in FIG. 13 may have walls that have detectors attached tothem, and the lengths of those sub-elongated members may be such thatthe detector attached to one sub-elongated member may be placed in braintissue and may be useful for monitoring oxygen tension, while thedetector attached to the other sub-elongated member may be placed incerebrospinal fluid and may be useful for monitoring sodiumconcentration.

Placement of Electroencephalography Electrodes

As discussed above, detectors that are electroencephalography (EEG)electrodes may be introduced into the subarachnoid space in both thespinal and intracranial regions, and in brain tissue using the presentmethods. By way of explanation, in epilepsy treatment, it is oftendifficult to localize the site of a seizure focus. One technique used inparticularly difficult cases involves placement of EEG electrodes eitherdirectly on the surface of the brain (electrocorticography) or withinthe brain substance (depth electrode implantation). Since EEG monitoringinvolves detection of extremely weak electrical signals that are emittedfrom brain cells, elimination of interference from scalp muscles,elimination of signal resistance from the skull bone, and placement ofelectrodes closer to the brain tissue emitting those signals is one wayto increase the sensitivity and specificity of localization anddetection.

While increasing the sensitivity and specificity of epileptiformactivity detection, such techniques as electrocorticography and depthelectrode implantation have traditionally been invasive, requiringeither burr holes in the skull for depth electrode placement orcraniotomy for cortical array placement in electrocorticography. Ifbilateral monitoring is desired, bilateral burr holes or craniotomieshave been necessary.

However, using the present methods, which involve percutaneous access tothe subarachnoid space, usually in the lumbar region, followed byplacement of devices such as sheath 24 and catheter 42, EEG electrodeplacement may be achieved, for example, in the cerebral subarachnoidspace after entry via the foramen magnum. EEG electrodes may be placedon the surface of the brain or within brain tissue using the presentmethods.

In instances in which EEG electrodes take the form of detectors 112discussed above with respect to FIG. 17, multiple detectors may belinked with a single communication device (also discussed above) thattakes the form of a wire. Multiple wire and detector(s) combinations maybe placed during a single procedure, and the different wires may havedifferent diameters, different stiffnesses, or the like. Thus, arrays ofEEG electrodes may be placed on or within brain tissue to map out theelectroencephalogram from the deep brain structures. As an exemplarydescription of the manner of placing multiple EEG electrodes, a catheterhaving two passageways may be advanced to a desired location over aguidewire positioned in one of the two passageways. An EEG electrode maythen be placed in a desired location through the open passageway. Afterplacement, the catheter may be withdrawn over the guidewire, leaving theguidewire and the first EEG electrode in place. The catheter may then bereintroduced over the guidewire, and a second electrode placed in adesired location through the once-again open second passageway. Thisprocess may be repeated as many times as necessary.

In instances in which the EEG electrodes take the form of detectors 94discussed above with respect to, for example, FIG. 14, multipledetectors may be linked with a single communication device (as discussedabove) that takes the form of a wire, and multiple wire and detector(s)combinations may be attached to a device such as sheath 24 or catheter42. Furthermore, one or more wire and detector(s) combinations can beattached to guidewires such as guidewire 44 shown in FIG. 1.

Spinal and Cerebral Stimulation

There are situations in medicine and in research where it is desirableto deliver an electrical impulse to the brain and spinal cord. Using thepresent methods, an electrode suited to such stimulation may be placed,thereby enabling the application of electric current, heat, orcryothermal stimulation of a patient's tissue. Such electrodes may beconfigured the same way as detectors 94 and 112 discussed above—that is,they may be attached to, or placed within, the wall of a device such assheath 24 or catheter 42, or they may not be associated with a device,such as can be achieved using detector 112. Furthermore, a transmissiondevice such as a wire may be coupled to the electrode (and eitherattached to a device like sheath 24 or catheter 42, or not attached inthat fashion, depending on the application) to introduce the stimulatingsignal to the electrode. However, the stimulating signal may also beintroduced to the electrode via a wireless transmission. Furthermore, incertain embodiments in which a transmission device such as a wire isused, the wire may be linked to a station useful in delivering thestimulating signal, and that is located outside of the patient's body orimplanted within the patient, such as a station that is implanted in thesubcutaneous space of the patient. Such stations currently exist incardiac pacemakers and in transcutaneous neural stimulation devices usedfor pain control.

Implantation of Radioactive Pellets, or Beads, for Treatment of Tumors

The present methods can be used to implant radioactive pellets, or bead,into patients, in areas such as the brain, in order to irradiate atumor. While the use of radioactive pellets for tumor irradiation isknown, the placement of such pellets using the present methods is novel.As with all the other applications that may be achieved using thepresent methods, the placement of radioactive pellets may be monitoredunder direct MR visualization. Further, a series of pellets may beimplanted into patients using a smaller introduction apparatus than iscurrently utilized for placing the pellets using conventionaltechniques.

Ablation of Brain Lesions

In functional neurosurgery, it is sometimes desirable to create lesionsin the brain. This is seen in chronic pain syndromes, Parkinson'sdisease, and other settings. Current techniques for creation of theselesions involve CT- or MR-guided stereotaxis, in which a cryothermal orthermal ablation device is introduced to the desired location in thebrain via a burr hole in the skull that the neurosurgeon drills in theoperating room.

Using the present methods, a device (such as sheath 24 or catheter 42)or a guidewire (such as guidewire 44) may be introduced into thesubarachnoid space (for example, the spinal subarachnoid space) andadvanced as described above with respect to FIG. 1 to a desiredlocation. Energy, such as thermal energy or cryothermal energy, may thenbe applied either to an ablation device imbedded in or attached to thecatheter, sheath, or guidewire or to an ablation device introducedthrough the passageway of the catheter or sheath such that a lesion iscreated in the adjacent tissue, such as brain tissue. Other areas ofapplication include tumors that may be in locations that are eitherinaccessible via conventional techniques, or that require unacceptablemorbidity to approach them via conventional techniques. Such locationsmay include locations in the brain stem, the spinal cord, or in thesubarachnoid space. In cases in which the ablation device is attached toor embedded within a device or a guidewire, the ablation device may bepositioned at the end of the device or guidewire, or it may bepositioned at any suitable location along the length of the device orguidewire.

By using one or more imaging modalities to monitor the therapy resultingfrom the ablation may make it feasible to create a lesion, observepartial success, and enlarge the lesion without repositioning theintroducing device (such as catheter 42), or with minimal manipulationof the introducing device. Furthermore, tissue ablation achieved usingthe present methods may be performed in conjunction with conventionalsurgery such that lesions are created either before or afterconventional resections, either to enhance the resection preoperativelyor to improve margins of incompletely-resected lesions, or to provide analternate approach to large-scale resections in diseases with multiplebrain lesions such as metastatic disease from different forms ofmalignancy.

Accessing One or More Ventricles

In medicine, the ventricular system is frequently catheterized, bothtemporarily (ventriculostomy) and permanently (shunting). This occurs tocombat hydrocephalus, to monitor pressure and, less often, forintroduction of various medications or withdrawal of cerebrospinalfluid. However, the current neurosurgical approach requires placement ofa burr hole in the skull bone and insertion of the catheter through thebrain tissue—usually the frontal or parietal lobe—to access theventricles.

Using the present methods of percutaneous subarachnoid navigation, thelateral ventricles, the 3^(rd) ventricle, and the 4^(th) ventricle maybe accessed via medical devices such as catheter 42 or guidewire 44.Accordingly, using the present methods, at least one ventricle locatedwithin the head may be accessed. Imaging modalities may be used asdescribed above (and with all the movements of medical devices describedherein) to monitor the position of such devices as they approach andenter a ventricle.

Furthermore, using the present methods, at least one ventricle locatedwithin the head may be drained. For example, in applications involvingshunting, there will be a need for placement of a shunt component in theperitoneal cavity or venous return to the heart. This may beaccomplished using the present methods. Specifically, afterpercutaneously introducing a device (such as sheath 24 or catheter 42)into the spinal subarachnoid space at an entry location, the devicehaving a first passageway sized to slidably receive, and operate with,at least a guidewire, and advancing the device within the subarachnoidspace at least more than 10 centimeters from the entry location, or tofacilitate intracranial access with a second device introduced throughthe first passageway, one or more ventricles located within the head maybe accessed and/or drained. The draining may be achieved using acommercially available mechanism that spans a ventricle and a drainagelocation, and that acts as a one-way valve that allows that CSF andother fluid to flow in one direction—away from the ventricle orventricles in question.

Brain Biopsies

The brain is a very soft and gelatinous tissue once the membranesurrounding it (pia) is penetrated. Neurosurgeons resecting brain oftenuse a tubular apparatus attached to suction to aspirate brain tissuerather than cutting it with a scalpel or scissors. That quality of braintissue should lend it to biopsy by way of aspiration.

Using the present methods, a device may be introduced through thepassageway of a device such as catheter 42 or sheath 24 that may be usedto remove a part of the brain. For example, the device that may be usedto remove a part of the brain may be a traditional stereotactic devicethat is configured for introduction through the passageway of a devicesuch as catheter 42 or sheath 24.

Alternatively, a device such as catheter 42 or sheath 24 may be coupledto suction by was of a syringe or other mechanism, and used to retrievea sample of tissue located at the tip of the catheter or sheath. Anotherfeature of biopsies is that often multiple samplings of tissue arerequired to retrieve diagnostic material. Hence, it may be necessary toreposition the catheter or sheath for more than one biopsy sample. Oncethe device has been positioned the first time, it is desirable to avoidhaving to repeat the navigation that was performed to achieve initialpositioning. Thus, using an embodiment of the sheath or catheter thathas two passageways, an operator may be able to use the sheath orcatheter in the manner discussed above with respect to EEG electrodeplacement. That is, the sheath or catheter may be positioned proximate(i.e., near) a target area, suction may be applied to an open passagewayto retrieve a portion of the brain. The sheath or catheter may then beremoved along the guidewire used to initially facilitate placement(leaving the guidewire in position), and if the tissue sample isinadequate, the catheter or sheath can be repositioned over theguidewire and another biopsy sample can be obtained in a similar manner.Without the retention of the guidewire via the one of the twopassageways, it would be necessary to reposition from scratch, repeatingwhatever risk or difficulties were encountered during the first catheteror sheath placement.

Treating Neurologic Conditions

Using the present methods, genetic material may be introduced throughthe passageway of a device such as catheter 42 or sheath 24 and placedwithin a patient suffering from a neurologic condition in order toassist in treating that neurologic condition. Such genetic material mayinclude human stem cells.

Furthermore, neurologic conditions arising from pressure on cranialnerves may also be treated using the present methods. For example, thepresent methods may be used to perform microvascular decompressions. Insuch an application, a device (such as sheath 24 or catheter 42) may bepercutaneously introduced into the spinal subarachnoid space at an entrylocation, the device having a first passageway sized to slidablyreceive, and operate with, at least a guidewire; the device may beadvanced within the subarachnoid space at least more than 10 centimetersfrom the entry location, or to facilitate intracranial access with asecond device introduced through the first passageway; and a seconddevice (which may be described as “material”) may be introduced throughthe first passageway and placed between a vascular loop and one or morecranial nerves (which may take the form of placing the device proximatea cranial nerve) in order to relieve compression of the cranial nerve bythe vascular loop. Furthermore, a second device may be introducedthrough the first passageway and used to cut a nerve, such as a cranialnerve.

Vascular Coagulation or Cauterization

Using the present methods, vessels may be coagulated at the time ofsurgery, either because they are observed to bleed or in order toprevent bleeding. Specifically, a device (such as sheath 24 or catheter42) may be percutaneously introduced into the spinal subarachnoid spaceat an entry location, the device having a first passageway sized toslidably receive, and operate with, at least a guidewire; the device maybe advanced within the subarachnoid space at least more than 10centimeters from the entry location, or to facilitate intracranialaccess with a second device introduced through the first passageway; andan apparatus that is or that is like a “two-point” or “Bovie” apparatus(which are used in conventional surgery or neurosurgery) configured forintroduction through the first passageway may be introduced through thefirst passageway and used to coagulate a vessel.

In conventional surgery, a metallic electrode is applied to a bleedingvessel and a current is applied through the electrode that heats thetissue such that the vessel is cauterized. That cauterization isachieved with the “two-point” apparatus via approximation of the pointsof a forceps, thus completing the current loop. However, monopolarcautery apparatuses also exist, and may be configured for introductionthrough the first passageway of a device introduced as described above.

Thus an apparatus having a cauterization element and a transmissiondevice (such as a wire, an insulated wire, a wire loop, or an insulatedwire loop) connected to the cauterization element that is configured forattachment to a current-inducing apparatus may be used with the presentmethods to apply heat to a vessel, thereby cauterizing or coagulatingit. Alternatively, the apparatus may include a set of forceps positionedat the end of a guidewire as the cauterization element, which forcepswould function to open and close and act similarly to the forceps onconventional “two-point” devices. The apparatus should be configured forintroduction through the first passageway (as discussed above), or itshould be combined with one of the present devices, such as catheter 42or sheath 24, in the manner that detector 94 discussed above may beattached to device 90. The transmission device may be attached to one ofthe present devices (including a guidewire) in the same manner discussedabove with respect to wire 96. The transmission device that is part ofthis apparatus may be a wire loop that flares slightly after it exitsthe passageway through which it is introduced.

Hence, using the present methods, a device (such as sheath 24 orcatheter 42) may be percutaneously introduced into the spinalsubarachnoid space at an entry location, the device having a firstpassageway sized to slidably receive, and operate with, at least aguidewire; the device may be advanced within the subarachnoid space atleast more than 10 centimeters from the entry location, or to facilitateintracranial access with a second device introduced through the firstpassageway; and an the aforementioned apparatus configured forintroduction through the first passageway may be introduced through thefirst passageway, current may be introduced to the cauterizationelement, the cauterization element applied to a selected vessel tissue,and coagulation achieved.

Cadaver Studies

Materials and Methods

Two recently deceased, unembalmed male human cadavers were placed inprone positions. Using fluoroscopic guidance, lumbar punctures wereperformed in each subject at both the L3-4 and L4-5 interspaces using astandard, single-wall puncture angiography needle. A 0.038 inchguidewire was then introduced and directed superiorly. Subsequently, a 5French (F) angiographic dilator was advanced into the subarachnoid spaceover the guidewire to dilate the tract, and a 5 F arterial sheath wasplaced with its tip directed superiorly. In each cadaver, one sheath wassubsequently used for catheterization posterior to the spinal cord andthe other was used for catheterization anterior to the spinal cord.

Following sheath placement, angiographic techniques were applied to thesubarachnoid space. Specifically, under fluoroscopic guidance ahydrophilic-coated angle-tipped guidewire (Radifocus→Glidewire, Terumo,Inc., Tokyo, Japan, distributed by Meditech→Boston Scientific Corp.,Watertown, Mass.) was advanced with its tip directed either anteriorlyor posteriorly under operator control. Care was taken to maintain amidline position whenever possible, but it could not always bemaintained. The advancement was performed with inflation of thesubarachnoid space via saline infusion. The pressure of the infusion waseasily controlled via management of the height of the flush bag abovethe patient's spine, though the pressures of the infusion and of thesubarachnoid space were not specifically monitored.

After entering the cranial space, manipulations with the catheters wereundertaken to explore areas for catheterization. Followingcatheterization manipulations, the catheters were left in place forsubsequent dissection. The sheaths were cut at the skin with theintroducers and microcatheters in place using standard wire cutters. Thestumps of the systems were then oversewn and the cadavers were embalmed.

Following embalming, one cadaver was examined for evidence of spinalcord injury from the catheterization process. Laminectomy was performedthroughout the cervical and thoracic spine and extended inferiorly tothe point of catheter entry. The opened dura was photographed with thecatheters in place. The spinal cord was removed and photographed withthe ventral catheter in place. Brain dissections were performed toconfirm catheter locations and to examine for unanticipated injury tobrain tissue, with specific attention to the optic chiasm region in thecase of catheters which passed through that region.

Results

In each case, the guidewire advanced relatively easily through thethoracic and cervical spine. In some cases, the catheter was advancedreadily without guidewire placement. Once at the foramen magnum,attempts were made with the posterior catheters to enter the 4^(th)ventricle. Observation was made during these attempts that navigation ofthe retrocerebellar space in the posterior fossa occurred relativelyeasily, on some occasions circum-navigating the posterior fossa to aposition anterior to the pons. Also, advancement superiorly behind thecerebellum to the level of the tentorium occurred relatively easily. Ineach cadaver, a tough membrane was encountered at the base of the skullwhen midline catheterization was attempted. Whereas deflection of theguidewire for lateral or posterior catheterization occurred easily, thesoft tip of the guidewire was inadequate for penetration of the membranein the midline and the stiff end of the guidewire was used to penetratethe membrane. Subsequently, catheterization superiorly proceeded easily.In Cadaver 1, the posterior fossa catheter ultimately traversed thecerebellum during an attempt at fluoroscopically-directed 4^(th)ventricular catheterization. In Cadaver 2, the 4^(th) ventricle wassuccessfully catheterized and injected with contrast, as describedbelow.

Attempts were made without complete success to determine the location ofthe 4^(th) ventricle using only fluoroscopy. Contrast injectionsresulted in intracranial spilling of contrast without outline ofcerebellar structures. Blind passes with the catheter to where the4^(th) ventricle should be resulted in successful catheterization of the4^(th) ventricle in one of the two subjects. This was confirmed withcontrast injection showing filling of the 4^(th) ventricle, retrogradeflow into the aqueduct of Sylvius, flow into the 3^(rd) ventricle, andsubsequent flow into the frontal horns of the lateral ventriclesbilaterally via the foramina of Munro.

In both subjects, catheterization of the subarachnoid space anterior tothe pons occurred easily. Catheters as large as 5 F were successfullyadvanced to this position. At the upper pontine level, a tough membranewas encountered in both subjects that would not permit highercatheterization using standard techniques. In both cases, the guidewirewas deflected repeatedly from that location, regardless of multiplecatheter repositioning attempts. Therefore, the guidewire was reversedand the stiff end of the guidewire was used to “punch” through thismembrane. The membrane was believed to be the membrane of Lilequist,though this could not be confirmed with certainty subsequent to thedissection. Once it was crossed, catheterization to the suprasellarcistern with the standard end of the microguidewire (Radifocus™ GuideWire M, Terumo, Inc., Tokyo, Japan, Tapered Glidewire Gold™ 0.018-0.013inches, distributed by Target Therapeutics→Boston Scientific Corp.,Fremont, Calif.) proceeded smoothly. A Transit® 18 microcatheter(Cordis® Endovascular Systems, Johnson & Johnson, Miami Lakes, Fla.) wasused in most cases, using in some cases a Tracker™ 38 catheter (TargetTherapeutics® Boston Scientific Corp., Fremont, Calif.) as a guidecatheter. In Cadaver 1, a single 4 F introducer catheter was used thatcame from a company bought by Medtronics (MIS, Inc., Sunnyvale, Calif.)that is now no longer commercially available. With that catheter, theintroducer catheter was advanced to the suprasellar cistern.

Once in the suprasellar cistern in Cadaver 1, advancement of thecatheter was relatively easy, and catheterization of the sylvian fissurewas observed and confirmed when contrast was injected and seen to flowdependently within the fissure. The catheter was left in that positionand the subject was embalmed.

In Cadaver 2, catheterization of the suprasellar cistern was followed byexperimentation regarding the degree of control had over placement.First, the frontal fossa on the side opposite from the previouslycatheterized middle fossa was catheterized. The catheter was advancedalong the orbital roof and observed to curve superiorly, with its tipultimately anterior to the frontal lobe and deep to the frontal sinus.The catheter was then withdrawn to the location on the orbital roof andthis was confirmed with contrast injection. Next, that catheter wasrepositioned and the contralateral floor of the middle cranial fossa wascatheterized and confirmed with contrast injection.

The posterior fossa catheter was then advanced and seen to be in the4^(th) ventricle, as described above. After contrast injection, someopacification of the 3^(rd) ventricle was seen. This opacification wasused as a “road map” for the anteriorly placed catheter and attemptswere made to catheterize the 3^(rd) ventricle directly through theregion of the interpeduncular cistern (with fluoroscopy, the exactposition was not identified). The pial lining of the undersurface of thebrain resisted perforation with the soft end of the guidewire and theventricle was elevated by the attempt but not punctured. Ultimately,however, the 3^(rd) ventricle was entered successfully, as evidenced bydrainage of the retained contrast. This was subsequently confirmeddirectly by contrast injection through the 3^(rd) ventricular catheter.This subject was then embalmed.

Cadaver 1 was the only subject in which the spinal component of thecatheterization was examined anatomically. Following full spinallaminectomy from the upper cervical area to the area of puncture in thelumbar spine, the posterior dura was incised and reflected. The dorsalintroducer catheter was seen lying superficial to the spinal cordwithout apparent spinal cord violation or laceration. This was thenremoved and the spinal cord was resected by cutting the nerve rootsbilaterally and lifting it out, retaining the ventral catheter with thespinal cord. It was observed to traverse anterolaterally, weavinganterior and posterior to different nerve roots. Again, there was noapparent spinal cord violation or laceration.

In Cadaver 1, anatomic exposure of the brain was preceded by lateximpregnation of the vasculature following decapitation, with arteriesimpregnated with red latex and veins impregnated with blue latex.Dissection was performed via extensive bone drilling of the leftfrontotemporal area to reproduce an expanded surgical approach to thesylvian fissure and the region of the basilar apex. Exposure using anoperating microscope revealed the microcather anterior to the midbrain,between the clivus and midbrain. It was followed inferiorly as itmigrated to the right side of the basis pontis. There was no apparentviolation of cerebral structures by the catheter during its passageanterior to the brain stem. The catheter traversed laterally in a sulcusin the left sylvian fissure. Removal of the temporal lobe revealed thecatheter in the sylvian fissure, near branches of the middle cerebralartery. The posterior fossa catheter was observed to enter thecerebellum and was not pursued via further detailed dissection.

Dissection of Cadaver 2 revealed the 3^(rd) ventricular catheter to bein place as suspected from the radiographs, located within the 3^(rd)ventricle. The catheter was seen passing anterior to the brain stemalong the clivus without brain stem penetration. Also, the basilarartery was seen separate from the catheter. The point of penetration ofthe 3^(rd) ventricle was essentially vertical in the midline from theinterpeduncular cistern. The 4^(th) ventricular catheter was under sometension and sprang laterally as the cerebellum was split in the midlineand its exact location could not be reconstructed. However, based on theimages during contrast injection, it appeared to lie in the cerebellartissue in the roof of the 4^(th) ventricle.

All of the present methods and devices disclosed and claimed herein canbe made and executed without undue experimentation in light of thepresent disclosure. While the this invention has been described in termsof specific embodiments, the described embodiments are not exhaustive,and it will be apparent to those of skill in the art that othervariations exist. For example, the flexible member portion that extendsaway from a skin-attachment apparatus (and thus away from a patient)should enhance robotic applications in angiography similarly to theirenhancement of robotic access of the subarachnoid space. Also, theflexible member portion enables angiographic applications in which thesheath is placed in a femoral artery and the patient is rolled into asupine position for intraspinal or other surgical access posteriorlywhile retaining anterior arterial access for angiography via theflexible member portion, which can be placed out from under the patient.

REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated herein by reference.

-   Amar et. al., “Microcatheterization of the cervical epidural space    via lumbar puncture: Technical note,” Neurosurgery, 48(5):1183-1187,    2001.-   Eguchi et. al., “Endoscopy of spinal cord and posterior fossa by a    lumbar percutaneous approach: endoscopic anatomy in cadavers,”    Minim. Invas. Neurosurg., 42(2):74-78, 1999.-   Fries et. al., “Biportal neuroendoscopic microscurgical approaches    to the study of subarachnoid cisterns. A cadaver study,” Minim.    Invas. Neurosurg., 39(4):99-104, 1996.-   13; Stefanov et. al., “A new method for transcutaneous coaxial    neuroendoscopy,” Anat Embryol (Berl), 194(4):319-26, 1996.-   Uchiyama et. al., “Ultrafine flexible spinal endoscope (myeloscope)    and discovery of an unreported subarachnoid lesion,” Spine,    23(21):2358-2362, 1998.-   U.S. Pat. No. 5,085,631.-   U.S. Pat. No. 5,470,318.

1. A method of achieving intracranial access from an entry location inspinal subarachnoid space, comprising: introducing a guidewire into thespinal subarachnoid space; introducing a device over the guidewire andinto the spinal subarachnoid space; advancing the device from the spinalsubarachnoid space into the intracranial subarachnoid space; introducinga penetration apparatus through the device; puncturing the pia materusing the penetration apparatus; advancing an electrode through thedevice and through the pia mater; and placing the electrode on or inbrain tissue.
 2. The method of claim 1, further comprising: applyingelectric current to the brain tissue with the electrode.
 3. The methodof claim 2, where the electrode is linked to a wire through a signal canbe sent to the electrode to cause application of the electric current.4. The method of claim 2, where a signal is wireless sent to theelectrode to cause application of the electric current.
 5. The method ofclaim 1, further comprising: applying heat to the brain tissue with theelectrode.
 6. The method of claim 5, where the electrode is linked to awire through a signal can be sent to the electrode to cause applicationof the heat.
 7. The method of claim 5, where a signal is wireless sentto the electrode to cause application of the heat.
 8. The method ofclaim 1, further comprising: applying cryothermal stimulation to thebrain tissue with the electrode.
 9. The method of claim 8, where theelectrode is linked to a wire through a signal can be sent to theelectrode to cause the cryothermal stimulation.
 10. The method of claim8, where a signal is wireless sent to the electrode to cause thecryothermal stimulation.
 11. The method of claim 1, where thepenetration apparatus includes an outer sleeve element and an innerpuncture element, and the outer sleeve element and the inner punctureelement are slidably coupled together.
 12. The method of claim 11,further comprising: applying electric current to the brain tissue withthe electrode.
 13. The method of claim 12, where the electrode is linkedto a wire through a signal can be sent to the electrode to causeapplication of the electric current.
 14. The method of claim 12, where asignal is wireless sent to the electrode to cause application of theelectric current.
 15. The method of claim 11, further comprising:applying heat to the brain tissue with the electrode.
 16. The method ofclaim 15, where the electrode is linked to a wire through a signal canbe sent to the electrode to cause application of the heat.
 17. Themethod of claim 15, where a signal is wireless sent to the electrode tocause application of the heat.
 18. The method of claim 11, furthercomprising: applying cryothermal stimulation to the brain tissue withthe electrode.
 19. The method of claim 18, where the electrode is linkedto a wire through a signal can be sent to the electrode to cause thecryothermal stimulation.
 20. The method of claim 18, where a signal iswireless sent to the electrode to cause the cryothermal stimulation. 21.A method of achieving intracranial access from an entry location inspinal subarachnoid space, comprising: introducing a guidewire into thespinal subarachnoid space; introducing a device over the guidewire andinto the spinal subarachnoid space; advancing the device from the spinalsubarachnoid space into the intracranial subarachnoid space; introducinga penetration apparatus through the device; puncturing the pia materusing the penetration apparatus; advancing a detector through the deviceand through the pia mater; and placing the detector on or in braintissue.
 22. The method of claim 21, where the detector is anelectroencephalography electrode and the method further comprises:monitoring electrical activity using the electroencephalographyelectrode.
 23. The method of claim 21, where the detector is a sensorand the method further comprises: monitoring a biochemical propertyusing the sensor.
 24. The method of claim 23, where the biochemicalproperty comprises pH, glucose concentration, oxygen tension, carbondioxide concentration, or sodium concentration.
 25. The method of claim21, where the detector is a thermal sensor and the method furthercomprises: monitoring temperature using the sensor.
 26. The method ofclaim 21, further comprising: monitoring neurotransmitter concentrationusing the detector.
 27. The method of claim 21, where the detectorincludes an anchoring mechanism.
 28. A method of achieving intracranialaccess from an entry location in spinal subarachnoid space, comprising:introducing a guidewire into the spinal subarachnoid space; introducinga first device over the guidewire and into the spinal subarachnoidspace; advancing the first device from the spinal subarachnoid spaceinto the intracranial subarachnoid space; introducing a penetrationapparatus through the first device; puncturing the pia mater using thepenetration apparatus; advancing a second device through the firstdevice and through the pia mater; and positioning the second deviceproximate the brain, the ventricular system, or a cranial nerve.
 29. Asheath comprising: a first sheath member having a first passageway, afirst length, and a first proximal end defined by a first valveapparatus configured to seal the first passageway, the first passagewayhaving a first passageway diameter at a location in the firstpassageway; and a second sheath member coupled to the first sheathmember, the second sheath member having a second passageway and a secondlength, the second passageway having a second passageway diameter at alocation in the second passageway; where the first passageway and thesecond passageway are separate from each other and not co-axial, thefirst length is different from the second length, and the first andsecond sheath members are positioned beside each other for a portion oftheir first and second lengths.
 30. The sheath of claim 29, where thefirst passageway diameter is different from the second passagewaydiameter.
 31. The sheath of claim 29, where the first passagewaydiameter is the same as the second passageway diameter.
 32. The sheathof claim 29, where the first length is greater than the second length,and the first passageway diameter is greater than the second passagewaydiameter.
 33. The sheath of claim 29, where the first length is greaterthan the second length, and the second passageway diameter is greaterthan the first passageway diameter.
 34. The sheath of claim 29, wherethe first sheath member has a first cross-sectional outer profile, thesecond sheath member has a second cross-sectional outer profile, and thefirst sheath member is coupled to the second sheath member with acoupling device that has a third cross-sectional outer profile that isdifferent from both the first and second cross-sectional outer profiles.